US2825203A - Aerodynamic valves - Google Patents

Description

J. H. BERTIN ETAL AERODYNAMI C VALVES y Filed June 24, y

INVENTORS M/f/MM Unite AERODYNMIC VALVES Jean H. Bertin, Neuilly-sur-Seine, and Alexandre A..R. G. Mihal, Asnieres, France, assig'ncrsto Societe Nationale (lEtude et de Construction de Moteurs dAviation, Paris, France, a' French company The applicants have already inventedand experimented with various aerodynamic valve devices, that is to say, ducts arranged in such manner` that their resistance to the flow of a gas in one direction is much smaller than the resistance to the flow thereof. in the opposite direction, the said ductsv thusbeing capable of acting as non-return valves while: being freely open andl comprising no movable member, whereby the .disadvantages inherentA inl such members are avoided.

Such aerodynamic valves are suitable more especially for co-ntrolling the admission of fresh' air into resonating or` non-resonating -pulsatory' "combustion chambers, whether it be a question of the chambers of units called pulse-jet units, in which case the valve has the object of permitting the admission of atmospheric air between the successive combustione, but of preventing the escape of the gases of combustion in the opposite direction, or of chambers intended to feed turbines, in which case the valve will generally be situated between the delivery side of an air compressor and each combustion chamber, its function being to permit the passage of the air from the compressor towards the corresponding chamber, but to prevent delivery of the gases from the chamber towards the compressor.

The aerodynamic valve forming the subject of the present invention arises out of observation of the fact that the coefficient of viscosity of the high-temperature gases resulting from a combustion is much higher than that of the fresh air, i. e. atmospheric air or air delivered by the compressor.

For example, in the case of a pulse-jet unit, the difference between the temperature of the hot gases which the aerodynamic valve is to stop and that of fresh air is about 2000 C. In this case, the ratio of the coeicients of absolute viscosity of the hot gases and of fresh air is about 3.8.

According to the invention, the aerodynamic valve comprises an assembly of small elemental ducts disposed in parallel, the total cross-sectional area of which ensures the required rate of flow of gas in the direction of free fiow, each of these ducts having, however, a sectional area sufiiciently small to make the pressure loss considerably greater in the case of high-temperature gas than in the case of relatively fresh gas.

The description which follows with reference to the accompanying drawings, which are given by way of nonlimitative example, will enable the manner in which the invention can `be carried into effect to be readily understood, the details appearing both from the drawings and from the text naturally forming part of the said invention.

Figure 1 shows in axial section a first constructional form of an aerodynamic valve according to the invention as applied to a pulse-jet unit.

Figure 2 is a transverse section of this valve on the line IIIL on a large scale.

Figure 3 shows a constructional modification of the aerodynamic valve.

.States Patent Figure 4 shows a second modification thereof.

Figure 5 sho-ws on a larger scale a detail vof this modification, and

Figure 6 is an axial section on a larger scale through a possible form for an elemental duct.

In the constructional form illustrated in Figure 1, there is shown at ll the combustion chamber of a pulse-jet unit, at 2 the orifice for the admission of atmospheric air, generally facing towards the front of the propelled craft,.and at 3 the nozzle in which' the combustion gases are ,expanded to supply a rearwardly directed propulsive jet.

The arrangement comprises a fuel injector I1 and an ignition device consisting, for example, of a sparkl plug 12, which may serve only for starting in the cas'e of a resonating arrangement in which the frequency of the successive combustions automatically adjusts itself to the frequency of the sound tube formed by the enclosed space of the arrangement,l the ignition at each combustiontheu taking place by the contact of the fresh carburetted mix turewith the residues of the preceding combustion.

There is disposed at 4 the aerodynamic valve, which must offer low resistance to the passage of air from 2 towards 1, but high resistance to the delivery of combustion gases from 1 towards 2.

Iny the example of Figure 1-, the said valve consists of a relatively thick` plate 5 having formed therein a number'of passages 6 of such small diameter that, by reason of the difference between the viscosity of the fresh air and that of the high-temperature gases resulting from the combustion, the pressure loss on the hot gases is much greater than the pressure loss on the fresh air, the flow of the gases from the chamber 1 towards the orifice 2 thus being substantially prevented.

Assuming that the temperature of the hot gases is 2280 K. and the rate of flow of the hot high-pressure gases through the passages 6 is equal to the speed of sound at this temperature, i. e. 750 m./s., calculation shows that good results will be obtained by giving the diameter of each passage 6 a value smaller than P being the maximum static pressure in the chamber 1 during the combustion. This correspo-nds to a Reynolds number lower than 2000 for the hot gases.

The number of passages 6 provided will naturally be such as to allow of obtaining the required rate of air feed.

Many other constructional forms may be conceived within the scope of the invention, which covers all clusters of elemental passages each having a small crosssectional area of throughflow so as to utilise the fact that the frictional forces for hot gases are greater than that for gases at lower temperature.

Thus, in the constructional modification shown in Figure 3, the aerodynamic valve c-onsists of a cluster of juxtaposed cylindrical tubes 7 of small diameter. These tubes may be connected together by a wire binding 8 and the whole assembly (which is shown in perspective in Figure 3) may be mounted between the air-admission orifice 2, and the chamber 1. It is not necessary, and is even undesirable, to close the gaps between the cylindrie-al tubes because these gaps also constitute elemental passages of small section.

Figure 4 shows another modification in transverse section (similar to that of Figure 2). The elemental passages are here formed between parallel plates 9 stacked parallel to the axis of the chamber 1. These plates are maintained at a small distance apart by covering each second plate with a winding 10 of wire of small diameter, the pitch of the Winding being such as to obtain the required small section for each elemental passage defined ik by two adjacent plates 9and by two contiguous convolutions of the winding 10.

Many other constructions are naturally possible.

Hitherto, the section of a passage has been assumed to be constant from end to end, but since the pressure of the hot gases which tend to escape through the elemental passages decreases from the chamber, as also does the Reynolds number, there is nothing to prevent the section of each elemental passage from increasing in proportion as it extends away from the chamber.

Figure 6 thus shows the section of an elemental passage of revolution, having a form diverging from the chamber 1 towards the inlet orice 2 for the atmospheric air. Each passage could also be given a conical form or any other form of increasing section from the chamber towards the outside.

Naturally, theapplicationto pulse-jetunits has only been indicated by way of `example and is in no way limitative.

The invention is applicable in all cases where it is desired to permit the ow of gas at relatively low temperature `in one direction, but to prevent the flow of gas at much higher temperature in the opposite direction.

It has alreadybeen proposedto apply pulsatory combustion chambers to the feeding of gas turbines.

What we claim is:

1. In a pulse jet unit having a resonant tiring combustion chamber, a valveless unilaterally conductive air inlet device for said chamber of the type oiering a greater resistance to the backlow of hot gases from said combustion chamber than to the flow of fresh air thereinto, said device comprising a plurality of piled up plates, spaced from and substantially parallel to each other, and a wire wound round every other plate with spaced turns, said wires contacting and separating relatively adjacent plates, whereby passages are bounded between adjacent plates and successive turns of wire.

2. A device as claimed in claim 1, wherein the winding is of substantially uniform pitch, with substantially parallelportions on each side of the plate.

References Cited in the tile of this patent UNITED STATES PATENTS 403,294 Schmid et al. May 14, 1889 1,448,151 Reeves Mar. 13, 1923 1,503,371 Meyer July 29, 1924 1,515,408 Puffer Nov. 11, 1924 1,852,164 Holzwarth Apr. 5, 1932 2,347,903 Gluck et al. May 2, 1944 2,523,308 Kemmer et al Sept. 26, 1950 2,551,112 Goddard.y May 1, 1951 2,618,925 Wislicenus Nov. 25, 1952 2,633,703 Tenny et al. Apr. 7, 1953 2,639,580 Stuart May 26, 1953 2,731,795 Bodine, Jr. Jan. 24, 1956 FOREIGN PATENTS 22,103 Norway Apr. 1, 1912 71,759 Sweden Apr. 30, 1928

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